Not everyone is good at having the discipline to get work done at home and to separate home and work while they're at home. Also, people with young children are naturally going to have a big problem. Lots of people who try it complain that their spouses and kids won't leave them alone at home, thinking that popping in isn't a big deal even though it interrupts their focus. And not everyone can afford a home that gives them extra space for a home office. Most people in Silicon Valley can't seem to afford anything bigger than a telephone booth. Don't forget that many people have roommates too.

There's a reason that coworking or small office spaces are so popular these days: for $500/month in many places, you get your own little office with a door that shuts where you can concentrate on your work, or a quiet cubicle among other people with similar situations. If everyone was able to make working at home work for them, these places would not exist.